I've been annoyed at the text rendering on OSX forever, but I finally got around to improving it. Previously it was trying to guess advance from the glyph bounding box, so narrow characters generally got jammed up against whatever followed them. It's still not perfect - CCS doesn't work and there's no kerning, but that would require changing to a line-at-a-time rendering model.

Strangely I find the old behaviour easier to read in places, with the new behaivior "Commodore" looks almost like it's been split into 2 words "Com modore" is that correct? Looks like there's far too much space between the 2 m characters. Or have you just got the screenshots swapped?

Forgive my ignorance, but what front end is that? (assuming it's a front end, that is...)

MewUI, the built-in MAME front-end. You see it when you launch MAME without a system name on the command line. Specifically, this commit fixes a bunch of text rendering issues in MAME's internal UI on OSX. I was trying to update the Japanese translation, and it was so bad I had to do something about it. It's bad enough in English, but Japanese was unusably bad.

Here's Japanese in 0.188:

Note how the characters are jammed up against the colons and Japanese comma, half-width space is far too big, the digit 1 is jammed up against whatever comes after it, small kana don't get a whole character space like they should, full-width spaces aren't rendered at all, lowercase i is jammed up against whatever comes after it, etc.

Here's Japanese in latest head:

It doesn't make you want to puke the moment you see it, and it's all legible.